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arXiv · 1601.07636

Probing neutron-proton dynamics by pions

Natsumi Ikeno·Akira Ono·Yasushi Nara·Akira Ohnishi
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Abstract

In order to investigate the nuclear symmetry energy at high density, we study the pion production in central collisions of neutron-rich nuclei ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ at 300 MeV/nucleon using a new approach by combining the antisymmetrized molecular dynamics (AMD) and a hadronic cascade model (JAM). The dynamics of neutrons and protons is solved by AMD, and then pions and $Δ$ resonances in the reaction process are handled by JAM. We see the mechanism how the $Δ$ resonance and pions are produced reflecting the dynamics of neutrons and protons. We also investigate the impacts of cluster correlations as well as of the high-density symmetry energy on the nucleon dynamics and consequently on the pion ratio. We find that the $Δ^-/Δ^{++}$ production ratio agrees very well with the neutron-proton squared ratio $(N/Z)^2$ in the high-density and high-momentum region. We show quantitatively that $Δ$ production ratio, and therefore $(N/Z)^2$, are directly reflected in the $π^-/π^+$ ratio, with modification in the final stage of the reaction.

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Natsumi Ikeno, Akira Ono, Yasushi Nara, Akira Ohnishi. 2018-04-05. Probing neutron-proton dynamics by pions. https://doi.org/10.1103/physrevc.93.044612

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